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Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2012 Cheyne-stokes respiration in patients with heart failure: prevalence, causes, consequences and treatments Brack, Thomas; Randerath, Winfried; Bloch, Konrad E Abstract: Cheyne-Stokes respiration (CSR) is characterized by a pattern of cyclic oscillations of tidal volume and respiratory rate with periods of hyperpnea alternating with hypopnea or apnea in patients with heart failure. CSR harms the failing heart through intermittent hypoxia brought about by apnea and hypopnea and recurrent sympathetic surges. CSR impairs the quality of life and increases cardiac mortality in patients with heart failure. Thus, CSR should actively be pursued in patients with severe heart failure. When CSR persists despite optimal therapy of heart failure, noninvasive adaptive servoventilation is currently the most promising treatment. DOI: https://doi.org/10.1159/000331457 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-60146 Accepted Version Originally published at: Brack, Thomas; Randerath, Winfried; Bloch, Konrad E (2012). Cheyne-stokes respiration in patients with heart failure: prevalence, causes, consequences and treatments. Respiration, 83(2):165-176. DOI: https://doi.org/10.1159/000331457 Cheyne-Stokes Respiration in Patients with Heart Failure: Prevalence, Causes, Consequences and Therapies Thomas Bracka, Winfried Randerathb and Konrad E. Blochc a Department of Internal Medicine, Kantonsspital, 8750 Glarus, Switzerland Institute for Pneumolgy, University Wittten/Herdecke and Clinic for Pneumology and Allergology, Centre of Sleep Medicine and Respiratory Care, Bethanien Hospital, solingen, Germany c Department of Pulmonary Medicine, University Hospital, 8091 Zurich, Switzerland b PD Dr. med. Thomas Brack Chefarzt Klinik für Innere Medizin Kantonsspital 8750 Glarus, Switzerland Tel. 055 646 32 01 Fax 055 646 43 02 e-mail : [email protected] Abstract Cheyne-Stokes respiration (CSR) characterizes a pattern of cyclic oscillations of tidal volume and respiratory rate with periods of hyperpnea alternating with hypopnea or apnea in patients with heart failure. CSR harms the failing heart through intermittent hypoxia brought about by apneas and hypopneas and recurrent sympathetic surges. CSR impairs the quality of life and increases cardiac mortality in patients with heart failure. Thus, CSR should actively be pursued in patients with severe heart failure. When CSR persists despite optimal therapy of heart failure, non-invasive adaptive servo-ventilation is currently the most promising treatment. Introduction Sleep disordered breathing (SDB) is common in patients with congestive heart failure (CHF) and SDB is increasingly recognized as an independent risk factor for morbidity and mortality in these patients [1]. This review focuses on Cheyne-Stokes respiration (CSR), a pattern of waxing and waning of ventilation with periods of hyperpnea alternating with central apnea/hypopnea in heart failure patients. CSR is also observed in certain patients with cerebro-vascular strokes [2] and in patients with pulmonary hypertension [3]. Typical features of CSR, the particular type of periodic breathing associated with heart failure, are a long duration of the hyperpnea phase and of the cycle time (figure 1) which are linked to the prolonged lung to chemoreceptor circulation time in low cardiac output states [4]. CSR is often observed during sleep and 1 is also termed central sleep apnea but CSR may as well emerge during wakefulness and even during physical activity [5] (Figure 1) [6,7]. Therefore, CSR in the context of chronic heart failure may be considered a syndrome distinct from other clinical conditions that are also associated with periodic central sleep apnea such as the idiopathic central sleep apnea syndrome or high altitude periodic breathing [8]. Since its first description in a patient suffering from heart failure with atrial fibrillation and a stroke two hundred years ago, CSR has been considered an ominous sign of the gravity of the underlying disease and as a forecast of the looming death. In the meantime, scientific evidence has accumulated to prove that CSR harms the failing heart. Quality of life and sleep as well as ventricular function suffer from frequent periodic breathing and CSR has been identified to shorten the life of heart failure patients. Pharmacological and non-pharmacological therapies are able to suppress or counteract CSR and treatment has been shown to improve ventricular function as well as quality of life [1,5]. Non-invasive ventilation, including continuous pressure support (CPAP), appears currently to most powerfully counteract CSR but the jury is still out if non-invasive ventilation may also prolong the life of heart failure patients. We reviewed the current literature on prevalence, risk factors, consequences and therapies of CSR in patients with CHF. Prevalence and Importance of Heart Failure and Cheyne-Stokes Respiration About 0.5% of the general population and 16% of people older than 75 years suffer from heart failure, respectively. Severe heart failure causes about 20% of all hospital stays in the elderly and carries a mortality of about 45% per year, which is higher 2 than for most cancers [9,10]. Sleep apnea often accompanies and aggravates heart failure. The reported prevalence of sleep-disordered breathing (either central or obstructive sleep apnea) varies largely due to differences in patient selection and methodological issues. Most studies recruited outpatients from heart failure clinics, but some included hospitalized patients and the severity of heart failure, assessed either by echocardiography or clinically, varied widely. The apnea-hypopnea index (AHI) that defined sleep apnea ranged from 15 to 5/h and, accordingly, the prevalence varied from 47 % to 82% and from 21% to 66% for sleep disordered breathing and CSR in patients with CHF, respectively [2,3,11-21] (Figure 2). Thus, CSR is not limited to severe heart failure but may also occur at moderate stages of CHF with left ventricular ejection fraction between 35% and 45% with milder functional impairment (NYHA II). Although many studies reported a predominance of CSR in CHF patients, OSA was also quite common [22]. (Figure 2) In addition to left ventricular failure, CSR is also associated with right heart failure secondary to pulmonary hypertension [3] [23] and with cerebro-vascular stroke [2,24,25]. The highest prevalence of CSR occurred in hospitalized patients with severe CHF and/or stroke [2,5,26,27] (Figure 2). Risk Factors for CSR Oldenburg et al [20] recently screened 700 patients with CHF referred to a cardiology division for sleep apnea. Among those with a left ventricular ejection fraction (LVEF) of <40%, 40% had CSR/CSA. As compared to those without SDB, patients with CSR/CSA were slightly older, predominantly male and had more severe CHF as reflected 3 in a higher NYHA functional class and a lower LVEF. Elevated pulmonary capillary wedge pressure (PCWP) is associated with hypocapnia, and both have been identified as risk factors for CSR [28,29]. In addition patients with CSR had a higher prevalence of atrial fibrillation and a reduced exercise capacity[20]. Mared et al. [16] found age to be the most important risk factor for CSR. Consequences of CSR Patients with CHF are less physically active if CSR occurs [30]. In 22 patients with mild to moderate CHF, actimetry was recorded to monitor the circadian activity pattern over the course of 2 weeks. Half the patients had predominantly central sleep apnea. On average, patients with CHF and sleep apnea spent more time resting at night and were less active during the day. In addition, their sleep was frequently interrupted by movements presumably due to arousals associated with apneas [31]. CSR also impairs quality of life (QoL) in patients with CHF. Carmona-Bernal et al. [32] evaluated patients with and without CSR with two QoL questionnaires. The Minnesota Living with Heart Failure questionnaire focuses on domains such as physical activity, fatigue, social relations and mood that are typically affected by CHF. The Functional Outcome of Sleep Questionnaire evaluates domains affected by sleep disorders such as productivity, activity and vigilance. Both questionnaires revealed impaired QoL for patients with CSR highlighting the clinical relevance of CSR [32]. We have recently evaluated QoL of patients with CSR associated with idiopathic pulmonary hypertension. Sleep studies in 38 consecutive patients identified 4 patients with predominant OSA and 15 patients with CSR (AHI>10 cycles/h). Patients with CSR 4 had impaired QoL mainly in the physical domain as assessed with the Minnesota questionnaire as well as with the generic SF-36 questionnaire. Remarkably, patients did not perceive subjective daytime sleepiness or other symptoms that would have clearly suggested sleep apnea [3]. Other studies have also confirmed that subjective sleepiness is not a prominent symptom of patients with CSR. Pepperell et al. [33] randomly treated 30 patients with CSR due to CHF either with therapeutic adaptive servo ventilation (ASV) or with a sham treatment during 1 months. The baseline Epworth sleepiness score was nearly normal in both groups and did not change with treatment. In contrast, ASV revealed an improvement in the sleep resistance time although several patients had normal sleep resistance time from the beginning. In conclusion, patients with CSR often seem not to perceive excessive sleepiness. Additionally, CSR increases sympathetic nervous activity (SNA) that harms the failing heart. Solin et al. [34] measured urinary catecholamines as a marker of SNA in patients with CHF (LVEF<35%), OSA and healthy controls. CHF patients excreted more norepinephrine than patients with OSA or healthy subjects; CHF patients with CSR excreted the most norepinephine. Multiple regression identified the severity of CHF as reflected by pulmonary capillary wedge pressure and nocturnal hypoxemia as strong predictors of urinary catecholamine levels. Elevated SNA may immediately impair ventricular function so that Brain Natriuretic Peptide (BNP) as a marker of CHF has also been found to increase during the night in patients with CHF and CSR [35,36]. Sympathetic activity is increased during the hyperpneic phase of CSR and the heart seems to be most vulnerable for arrhythmia during hyperpnea [37]. 24 h ECG monitoring 5 revealed that patients with severe CSR had a significantly increased prevalence of nonsustained ventricular tachycardia and other arrhythmias as compared to patients with mild or no CSR [38]. In addition, patients with severe CSR had a reduced heart rate variability which suggests autonomic dysfunction [39]. A reduced percentage of beats with more than 50ms of RR interval variation was associated with mortality in HF patients in an earlier study [40]. Prognosis of patients with CSR and CHF Hanly et al. [41] reported a mortality of 86% and 56% in patients with heart failure and CSR compared to patients without CSR during a follow-up of 2 years, respectively. Javaheri et al. [42] recently found in a retrospective cohort study that both obstructive and central sleep apnea in heart failure patients were largely under diagnosed. Patients who were diagnosed and treated had a better 2-year survival than patients who were not tested (hazard ratio 0.33). The association of CSR with a two- to threefold increase in mortality sparked the hope that treatment of CSR would decrease mortality albeit other reports questioned an independent association of CSR and mortality in heart failure [19]. Autonomic dysfunction and cardiac electrical instability are potential explanations for the increased mortality in CHF patients with CSR. Lanfranchi et al. [43] observed 62 patients with severe CHF for a median of 28 months. Multiple regression revealed left atrial area (LA) measured by echocardiography and the number of CSR cycles per hour at night to be the most important independent predictors of transplantation free survival. For example, the estimated mortality of a patient with a LA area of 55 cm2 and 40 cycles/h of 6 CSR was more than four times higher than the mortality of a patient with similar LA area but no CSR. (Table 1) summarizes the most recent studies of the impact of CSR on survival in HF patients who were treated with all current standard cardiac medications [43] [5,19,21,44-46]. The outcome was either death or cardiac transplantation. The majority of studies found an increased mortality with a hazard ratio of 2.1 to 5.7 for CSR with only two exceptions [19,21]. Patients and methods varied between studies, which may explain the different outcomes. For example, the AHI cut-off that discriminated patients with and without CSR varied between 5 and 30/h. The patients’ mean LVEF was very low with one exception and the observation time ranged from 2.2 yrs to more than 4 years. Some studies excluded obese patients or those with atrial fibrillation and CSR was treated with oxygen or CPAP in three studies; two studies included daytime CSR. Corra et al. [45] studied patients with an EF<40% who underwent sleep studies as well as spiroergometry; patients were followed for a mean of 3 years. When controlled for clinical and echocardiographic severity of CHF, cumulative survival without cardiac events was most reduced in patients who had both CSR during the night and during exercise testing. CSR not only occurs during the night but also during the day. We recently found patients with severe heart failure to breathe periodically during about 10% of the daytime [5]. Continuous recordings of the breathing pattern in 60 patients with severe heart failure during their usual activities over 24 h at home revealed CSR to peak at 1pm, 5 pm and 3 am (Figure 3). Daytime CSR was associated with a higher mortality while nighttime CSR was not an independent predictor of survival during the observation time of more 7 than two years. Patients with daytime CSR had a nearly 4-fold increased mortality even when controlled for age, gender and severity of heart failure. Although data from the majority of studies suggests an independent effect of CSR on mortality in CHF, the association is not always strong. One reason for the variable association may be the varying prevalence of CSR within the same patient. Of 19 patients monitored over the course of 4 successive nights, 8 revealed a change in the severity of apnea from mild to severe if a cut-off of 30/h was selected and 8 changed their predominant type of apnea from CSR to OSA and vice versa [47]. Moreover, some patients change their apnea type within the same night; while OSA may prevail in the first part of the night, CSR often dominates in the second part [48]. Pathophysiology of Cheyne-Stokes Respiration Left heart failure that causes an increased pulmonary venous pressure is regarded as a source of CSR. The elevated pulmonary venous pressure leads to pulmonary congestion that stimulates the pulmonary stretch receptors, which heighten the sensitivity of peripheral chemoreceptors for CO2 through their vagal afferents [28,49,50]. Since CO2 sensitivity increases, patients begin to hyperventilate and the arterial CO2 (PaCO2) falls below the apnea threshold [51]. Moreover, the hypoxia that follows the apnea/hypopnea enhances the post-apneic hyperventilation. If chemical control prevails the cortical influence on the respiratory controller, as it typically occurs during sleep, patients become apneic until the PaCO2 rises again above the apnea threshold. Thus, the alternating pattern of apnea and hyperpnea continues due to oscillations of the PaCO2 8 around the apnea threshold [52,53]. This periodic respiratory over- and undershoot causes additional sympathetic stimulation in patients who are already sympathetically stimulated through their heart failure [54]. Recent work confirmed the key role of CO2 in the patho-physiology of CSR that primarily seems to be determined by the difference of the PaCO2 during steady state ventilation (i.e., the eupneic PaCO2) and the respective apnea threshold for CO2 [55,56]. Patients with high ventilatory equivalents for CO2 during exercise testing were particularly prone to CSR because the heightened ventilatory equivalent was an indicator of the increased chemo sensitivity for CO2 [57]. The augmented chemo sensitivity is likely caused by the pulmonary congestion because the pulmonary capillary occlusion pressure is inversely correlated with the PaCO2 during wakefulness [28,49]. Since in about 20% of patients CSR persists in an albeit milder form up to 12 months after heart transplantation, periodic breathing appears to result not only from pulmonary congestion but part of the pattern seems to be learned and engraved in the respiratory controller [58,59]. It has also become obvious that obstructive and central apneas are not strictly different entities but may share a common origin because obstructive apneas may dominate the first half of the night transforming to mainly central apneas towards the morning in the same patient [47,48]; in addition, the first breath of hyperpnea often has an obstructive component during CSR [60]. 9 Therapy of Cheyne-Stokes Respiration Treatment of the underlying heart disease CSR fuels the vicious cycle of heart failure through recurrent sympathetic over stimulation and intermittent hypoxia so that the transformation of periodic into regular breathing has been a longstanding aim of cardiac therapy [61]. Primarily, the pharmacological and interventional therapies aim to ease pulmonary congestion through a decrease in preload and afterload e.g. with diuretics and ACE-inhibitors, to lessen sympathetic over stimulation through the blockade of 1-receptors, or to optimize cardiac output by electrical stimulation. Walsh et al. [62] found the ACE-inhibitor captopril to improve sleep apnea and sleep quality in heart failure patients. Carvedilol, a beta-blocker commonly used for the treatment of congestive heart failure, has been demonstrated to reduce CSR in patients with CHF [63]. Atrial overdrive pacing was reported to reduce CSR in patients with heart failure, but these results could not be reproduced by several consecutive studies [64-67]. Cardiac resynchronization with biventricular pacemakers has repeatedly been reported to more than halve CSR in patients with severe heart failure and ventricular asynchrony. Kara et al. [68] found a significant improvement of central sleep apnea under active stimulation with atrial synchronized biventricular pacemakers in 12 patients with HF and left ventricular ejection fraction of 28 ± 2.8%. Cardiac resynchronization therapy has been shown to also improve sleep quality, quality of life as well as cardiac pump function and patients´ outcome. Therefore, this albeit very expensive therapy should be evaluated in patients with severe heart failure associated with ventricular asynchrony due to conduction abnormalities [69]. If the cardiac therapy 10 fails to reverse CSR, directly influencing the respiratory controller to smooth the periodic breathing arises as the goal of therapy [9,10,70]. Pharmacotherapy of CSR Theophylline increases the respiratory drive and improves myocardial contractility so that periodic breathing decreases, but at the same time the drug doubles the serum concentration of renin, causes arrhythmias and possibly increases the risk of sudden death [71]. In a randomized study including 15 patients, the treatment with theophylline over 5 days improved CSR but not cardiac pump function [72]. Andreas et al. [73] demonstrated that theophylline did not increase sympathetic nerve activity in heart failure patients in contrast to healthy controls, but plasma renin level doubled in both groups. Theophylline is therefore currently not recommended as a treatment of CSR. Acetazolamide is a carboanhydrase inhibitor that causes renal loss of bicarbonate. The resulting metabolic acidosis stimulates respiration and reduces periodic breathing by increasing the difference between the eupneic PaCO2 and the respective apnea threshold. In a short randomized trial of 12 patients with heart failure, acetazolamide decreased periodic breathing by 38% and improved daytime sleepiness [56], but since long-term results are lacking, the drug may only be tried in selected patients under careful supervision. Respiratory disturbances might be aggravated by arousals which destabilize ventilation. In order to suppress arousals, Younes et al. applied pentobarbital in a placebo-controlled animal trial [74]. However, the authors found serious blood gas 11 alterations with prolonged hypoxia. Data on the suppression of arousals in humans are not yet available. Oxygen and Inhalation of Carbon Dioxide Supplemental oxygen increases the oxygen supply of the left ventricle and additionally may reduce the reflex activation of the peripheral chemoreceptors. Oxygen suppresses periodic breathing because it blunts the hypoxic respiratory drive and the consecutive hyperventilation. However, data from clinical studies show conflicting results. Thus, nocturnal oxygen applied over 1 to 4 weeks cut CSR by half, decreased nocturnal norepinephrine excretion and increased maximal oxygen uptake during exercise because of improved physical performance [75-78]. Conversely, Gold et al. [79] found that supplemental oxygen may increase frequency of obstructive apnoeas in patients with mixed sleep apnea. Moreover, left ventricular ejection fraction and the patients’ quality of life did not improve [75,77,78,80]. In contrast, recent studies also found nocturnal oxygen to improve quality of life and cardiac function in heart failure patients [81,82]. The CANPAP post hoc-analysis showed that optimal suppression of respiratory disturbances is crucial to lessen mortality in heart failure patients with sleeprelated breathing disturbances [83]. Since bilevel pressure support ventilation or adaptive servo-ventilation have been found to suppress CSR better than oxygen [84] oxygen may be reserved for patients who cannot tolerate non-invasive ventilation. Inhalation of supplemental CO2 or addition of artificial dead space suppresses CSR through a permanent elevation of PaCO2 above the apnea threshold [85-88]. In a recent trial including 6 patients without heart failure, Thomas et al. [89] found the 12 addition of computer controlled CO2 at an inspiratory concentration of 0.5 to 1% through a CPAP circuit very effective for the treatment of CSR. Since increased PaCO2 can cause sympathetic stimulation and because trials of long-term effects of CO2-augmentation are lacking, this therapy remains experimental [90]. The disadvantage of permanently elevated PaCO2 could eventually be overcome by dynamical application of low inspiratory concentration of CO2 as recently shown by Mebrate et al. [91] in a sophisticated computer model. Positive airway pressure ventilation Over the past ten years, the application of continuous positive airway pressure (CPAP) has repeatedly been shown to reduce CSR, to improve left ventricular function and to decrease nocturnal norepinephrine excretion in patients with heart failure [92-94]. CPAP increases the intrathoracic pressure, which decreases both the afterload by lowering transmural cardiac pressure and the preload by lowering the venous return, so that cardiac function improves in patients with high ventricular filling pressures [95-97]. Additionally, CPAP may interrupt CSR by counteracting the periodic oscillations of the end-expiratory lung volume during CSR [98]. In a randomized trial with 66 patients over 5 years, CPAP improved left-ventricular ejection fraction by 7% and decreased the combined rate of mortality and transplantation in the group of 29 patients with CSR while the 37 patients without CSR did not benefit from CPAP [44]. Based on these results, a large randomized multicenter trial containing 258 patients with heart failure and CSR was performed in Canada (CANPAP) [99]. 128 patients were treated with CPAP and were compared to 130 matched patients without CPAP therapy. CPAP reduced CSR, improved 13 nocturnal oxygen saturation, enhanced left-ventricular ejection fraction by 2%, reduced nocturnal norepinephrine excretion and also prolonged 6 min walking distance. Despite all these advantages of CPAP therapy, the treated patients had a lower transplant-free survival compared to untreated patients during the initial 18 months of the trial; after 18 months, survival rate was similar for both groups. The trial was precociously terminated because of the higher mortality of treated patients while mortality of untreated patients and patient recruitment was unexpectedly low. The converse effect of CPAP on mortality compared to the promising pilot study was explained by the improved pharmacological treatment of heart failure in the past years. The addition of beta-blockers that has become a mainstay of heart failure therapy in the period in-between the pilot study [44] and the CANPAP trial [99] may have weakened the harmful influence of CSR and its consecutive sympathetic over stimulation on the failing heart. Other reasons for the divergent results of the CANPAP trial compared to the preceding study may be the lower compliance of patients with CPAP (4.3 vs. 5.6 h/d), the lower CPAP pressure (8 vs. 10 cmH2O) and the lack of statistical power of the CANPAP trial because of the unforeseen low mortality of the control group [70]. In a post-hoc analysis, only the subgroup of patients in whom CPAP suppressed CSR successfully (AHI<15/h) benefited with increased left ventricular function and transplant free survival compared to patients who responded insufficiently (AHI>15/h) so that only good responders may profit from CPAP [83]. As a result of the CANPAP trial, CPAP cannot anymore be regarded as the standard therapy of CSR, but CPAP may still be beneficial for a subgroup of patients with high (>12 cmH2O) left-ventricular filling pressure and without atrial fibrillation [100,101]. As CPAP has been shown to improve survival in responders, a CPAP trial seem a reasonable 14 first step of ventilatory support for heart failure patients with CSR. However, this trial should closely be monitored and ASV should be used if CPAP fails. The disputed benefit of CPAP for the treatment of CSR and the patients’ problems with CPAP compliance has spawned interest in alternative modes of noninvasive ventilation. While CPAP maintains the same pressure level during expiration and inspiration, pressure support ventilation (PSV) operates on a lower pressure during expiration and a higher pressure that actively supports inspiration. Contrary to CPAP, pressure support ventilation has the option to ventilate the patient during apnea and to support the respiration during hypopnea. Pressure support ventilation can be applied in different algorithms for the treatment of CSR: bilevel positive airway pressure (BPAP) in spontaneous (S) or timed (T) or spontaneous/ timed (ST) mode, and adaptive servoventilation (ASV) Bilevel positive airway pressure modes apply a constant pressure support during inspiration. BPAP S only supports the patient´s spontaneous ventilation while BPAP T or ST apply mandatory breaths in case of breathing pauses. Therefore, BPAP ST or T actively ventilate the patient if his own ventilation is insufficient. They represent modes of non-invasive ventilation. Adaptive servo-ventilation (also named auto servoventilation or anticyclic modulated ventilation) supports inspiration minimally during hyperpnea and maximally during apnea/hypopnea so that based on sophisticated algorithms the pressure support acts anti-cyclically to the cycles of CSR. The expiratory pressure is manually or automatically titrated in order to eliminate obstructive breathing disturbances. Similar to BPAP ST/T, ASV devices also apply mandatory breaths in case of apnoeas [102]. 15 In a couple of small studies, BPAP ventilation in ST mode was somewhat better in suppressing CSR than CPAP [51,103]. Köhnlein et al. compared the efficacy of BPAP ST with CPAP in a cross-over study for two weeks each with a two weeks wash-out period in-between in patients with CSA and chronic congestive cardiac failure. Both modes improved respiratory disturbances, subjective and objective parameters of sleep quality and also left ventricular function with no significant difference between them [51]. Dohi et al. applied BPAP ST to a small group of patients who did not sufficiently respond to CPAP [104]. The authors showed a further reduction of respiratory disturbances in nine subjects. In contrast, Johnson et al. found that bilevel in ST or T mode was more likely to worsen than improve central breathing disturbances, including CSR [105]. As the body of evidence on bilevel therapy is very limited and the results are conflicting BPAP cannot generally be suggested for treatment of CSR. Compared to CPAP and BPAP, ASV more powerfully suppressed CSR; at the same time, sleep quality, quality of life, left ventricular function, and exercise capacity improved with ASV and norepinephrine excretion were suppressed [33,84,106-109]. Teschler et al. compared oxygen, CPAP, BPAP ST and ASV for one night each in a group of 14 patients [84]. Although BPAP ST showed a better improvement of the mean cental apnoea index (CAI) as compared to oxygen and CPAP, the individual results varied widely. In contrast, ASV normalised the CAI in almost all patients. Peperell et al. applied effective or sub-therapeutical ASV for one month in 30 patients with chronic heart failure and mainly CSR/CSA [33]. Effective ASV was superior in improving respiratory disturbances, daytime performance, cardiovascular and sympathetic markers. 16 Philippe et al. proved that ASV was superior to CPAP in terms of respiratory disturbances, heart function, quality of life, and compliance over 6 months [106]. In addition, Morgenthaler et al. showed that ASV was superior to BPAP ST in a heterogenous population of patients with CSA/CSR, complex sleep apnea and mixed sleep apnea [107]. ASV was also able to suppress CSR below 15 cycles/h in heart failure patients who remained refractory under CPAP and BPAP ventilation [110]. In clinical practice, many patients suffer from co-existing obstructive sleep apnea and CSR/CSA rather than pure CSR/CSA. In two prospective observational studies two different algorithms of ASV proved to effectively suppress all types of respiratory disturbances and to improve sleep quality as measured by sleep stages and arousals with no difference between patients with and without cardiovascular diseases [111,112]. Kasai et al. confirmed these results in a CPAP controlled trial over three months in 31 heart failure patients [113]. Since patients with CSR infrequently suffer from daytime sleepiness, compliance with positive pressure therapies is often low and therefore the finding that compliance with ASV was 2h/d higher than with CPAP is very important [106]. However, it seems crucially important to focus on problems with mask and interface. Pusalavidyasagar et al. described a higher prevalence of interface problems in patients with complex sleep apnoea [114]. Active or passive closure of the upper airways can be supposed if an increase of the pressure support is not able to overcome breathing disturbances [60]. These phenomena should be primarily considered in case of treatment failure with ASV [102,112]. Although preliminary data from a CPAP-controlled trial over twelve months in patients with heart failure showed a significantly greater improvement of central 17 breathing disturbances with ASV [115] large studies on survival and cardiovascular outcomes are lacking. Nevertheless, ASV currently appears to be the most promising mode of ventilation for the therapy of CSR. Conclusion CSR is highly prevalent and harmful for patients with CHF. Since the treatment of CSR has been shown to improve cardiac function and quality of life, sleep studies should be performed and treatment for CSR ought to be tried in patients with severe heart failure. Albeit the proof that treatment of CSR lowers mortality is pending, CSR should be treated to fight the debilitating symptoms of severe heart failure. Currently, adaptive servo-ventilation seems to be the most efficient therapy for CSR. Large randomized controlled trials of the long-term effects of ASV on morbidity and mortality in patients with severe heart failure and CSR are under way and their results are expected in the coming years. 18 References 1. Sharma B, Owens R, Malhotra A. Sleep in congestive heart failure. Med Clin North Am 2010;94:447-464. 2. Parra O, Arboix A, Bechich S, Garcia-Eroles L, Montserrat JM, Lopez JA, Ballester E, Guerra JM, Sopena JJ. Time course of sleep-related breathing disorders in firstever stroke or transient ischemic attack. 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Eur Respir J 34, 38s (abstract). 2009. 36 Figure legends Figure 1: Breathing pattern recorded in an ambulatory patient with severe heart failure by a portable device incorporating respiratory inductive plethysmography, pulse oximetry, ECG and an accelerometer. The left panel shows a period of walking, the right panel a period of quiet rest during daytime. Waxing and waning of the rib cage and abdominal excursions and of the minute ventilation derived from the calibrated inductance sensors reveal periodic breathing with subtle oscillations in oxygen saturation (SpO2). Modified from Brack et al. [5]. Figure 2: Prevalence of sleep apnea in patients with congestive heart failure, stroke or pulmonary hypertension and in a community sample of men older than 65 years. The data were retrieved from studies published by various authors indicated on the corresponding bars. Hatched and open columns represent the relative proportion of Cheyne-Stokes respiration/central sleep apnea (CSR/CSA) and of obstructive sleep apnea (OSA) , respectively. The cut-off levels of the apnea/hypopnea index (AHI) used for definition of sleep apnea are indicated. Severe congestive heart failure was defined by a left ventricular ejection fracture of less than 55 to 45%. In this group of patients, the prevalence of sleep apnea is very high (between 47% to 82%) due to a high prevalence of both, Cheyne-Stokes respiration and obstructive sleep apnea. Figure 3: Using portable monitoring devices in 60 ambulatory patients with severe congestive heart failure, the circadian prevalence of Cheyne-Stokes respiration was investigated. The highest number of Cheyne-Stokes breathing cycles occurred during the 37 night but Cheyne-Stokes respiration was also observed during daytime when patients were upright performing their usual daily activities. Patients with a high prevalence of daytime Cheyne-Stokes respiration (>10% of the daytime) had a much shorter survival without heart transplantation compared to patients with <10% of daytime with CheyneStokes respiration (hazard ratio 3.8). Modified from Brack et al. [5]. 38 Table. Prognostic significance of Cheyne-Stokes respiration in patients with heart failure Author, year of Lanfranchi publication 1999[43] Number of Sin Corra Javaheri Brack Roebuck Luo 2000[44] 2006[45] 2007[46] 2007[5] 2004[19] 2009[21] 62 66 133 88 60 78 128 death, Tx death, Tx death, Tx death death, Tx death death + + + + (+) - - 2.53 5.7 2.1 3.8 ≥30 ≥15 >30 ≥5 ≥15 >5 ≥5 23 22 23 24 26 20 36 2.3 2.2 3.2 4.3 2.3 4.3 2.9 Patients CSR CSR CSR CSR CSR with atrial treated during treated during treated patients Outcome Risk associated with CSR * Apnea/hypopnea index defining presence of CSR, 1/h Left ventricular ejection fraction, % Mean observation period, y Remarks fibrillation exercise excluded and sleep daytime * hazard ratio controlled for several confounders, with + and - denoting increased mortality and equal mortality of CSR vs. no CSR, respectively, Tx = survival without cardiac transplantation 39 Figure 1 40 Figure 2 41 Figure 3 42